An optical detection apparatus and method for detecting acetic anhydride content

Abstract

This invention provides an optical detection device and method for detecting acetic anhydride content, including a sample quantitative introduction module for quantitatively introducing the sample to be tested; a reagent storage module for storing non-aqueous solutions of ferric chloride, hydroxylamine chloride, perchloric acid-acetic acid, conditioning solution, colorimetric water, standard acetic anhydride solution, and blank base solution; a reagent instant preparation module; an anhydrous protection module for maintaining a low-moisture interference environment during the pre-reaction stage; a segmented reaction colorimetric module including a pre-reaction chamber and a colorimetric detection chamber, wherein the pre-reaction chamber is used to conduct a pre-reaction between the sample to be tested and the pre-reaction solution; and a quantitative water introduction module for adding a predetermined amount of colorimetric water to the colorimetric detection chamber after the pre-reaction is completed. This invention solves the problems of large visual colorimetric errors, poor process control consistency, and difficulty in balancing rapid detection and accurate quantification in the prior art.

Description

Technical Field

[0001] This invention relates to the field of acetic anhydride detection, and more particularly to an optical detection device and method for detecting acetic anhydride content. Background Technology

[0002] Acetic anhydride is a common reactant and residual component in fine chemicals, organic synthesis, and end-capping reactions. Its content directly affects product purity, subsequent reaction activity, and system stability; therefore, accurate detection of acetic anhydride content in samples is crucial. Current technologies for detecting trace amounts of acetic anhydride in acetic acid often employ a hydroxylamine-ferric colorimetric route. This involves sequentially mixing a non-aqueous solution of ferric chloride, a perchloric acid-acetic acid solution, and a non-aqueous solution of hydroxylamine chloride, then adding the sample to undergo a pre-reaction, followed by water for color development, and finally visually comparing the result with a standard solution to determine the acetic anhydride content. While this method has some practicality and provides relatively clear requirements for reagent ratios, pH values, pre-reaction time, and color development time, the result interpretation still relies on manual observation, making it susceptible to influences from ambient light, operator experience, and color discrimination ability. Furthermore, the consistency and automation of the detection are insufficient.

[0003] On the other hand, for complex matrix samples, existing technologies have also proposed quantitative approaches that use standard addition methods and ensure the same reaction time to establish a standard curve in order to improve the accuracy of the results. However, such approaches usually rely on more complex instrument analysis systems, which is not conducive to the miniaturization of equipment and rapid detection applications.

[0004] Therefore, existing technologies have at least the following problems: First, manual colorimetry is highly subjective and difficult to achieve stable, digital readings; second, existing detection processes are sensitive to anhydrous conditions, liquid addition order, reaction time, and colorimetric endpoints, and manual operation has insufficient repeatability; third, existing quantitative methods for complex matrices involve complex equipment and high costs.

[0005] Therefore, it is necessary to provide a new optical detection device for detecting acetic anhydride content to solve the above-mentioned technical problems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an optical detection device for detecting acetic anhydride content, which solves the problems of large visual colorimetric errors, poor process control consistency, and difficulty in balancing rapid detection and accurate quantification in the prior art.

[0007] The optical detection device for detecting acetic anhydride content provided by the present invention includes a sample quantitative introduction module for quantitatively introducing the sample to be tested; The reagent storage module is used to store non-aqueous solutions of ferric chloride, non-aqueous solutions of hydroxylamine chloride, perchloric acid-acetic acid solution, conditioning solution, colorimetric water, standard acetic anhydride solution, and blank base solution, respectively. The reagent instant preparation module is used to mix the non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution and the non-aqueous solution of hydroxylamine chloride in a set ratio to form a pre-reaction solution at the start of the detection. Anhydrous protection module is used to keep the pre-reaction stage in a low-moisture interference environment; The segmented reaction colorimetric module includes a pre-reaction chamber and a colorimetric detection chamber. The pre-reaction chamber is used to perform a pre-reaction with the sample to be tested and the pre-reaction solution. The colorimetric detection chamber is used to receive the reaction solution after the pre-reaction and form a colorimetric solution after adding colorimetric water. The quantitative water introduction module is used to add a set amount of colorimetric water to the colorimetric detection chamber after the pre-reaction is completed; The optical detection module is used to perform absorption optical detection on the colorimetric solution and output a detection signal; The endpoint determination module is used to determine whether the colorimetric reaction has reached a stable endpoint based on the changes in the detection signal. The control and data processing module is used to control the coordinated operation of each module and to calculate the acetic anhydride content in the sample to be tested based on the detection signal. The result output module is used to output the detection results; The control and data processing module includes at least a standard curve detection mode and a standard addition detection mode.

[0008] Preferably, the reagent instant preparation module includes a multi-channel micro-metering pump, a switching valve, a manifold node, and a mixing channel. The non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution, and the non-aqueous solution of hydroxylamine chloride are instantaneously mixed at the manifold node before entering the pre-reaction chamber to form a pre-reaction solution.

[0009] Preferably, the anhydrous protection module includes a sealed housing and at least one of a drying gas interface, a desiccant chamber, and a humidity detection unit disposed on the sealed housing, wherein the reagent instant preparation module and the pre-reaction chamber are disposed inside the sealed housing.

[0010] Preferably, the pre-reaction chamber and the colorimetric detection chamber are set independently and connected by a switching valve or a connecting microchannel. The pre-reaction solution completes the contact reaction between the sample to be tested and the pre-reaction solution in the pre-reaction chamber before being introduced into the colorimetric detection chamber. The colorimetric water is added only in the colorimetric detection chamber.

[0011] Preferably, the quantitative water intake module includes an independent water path, a micro-metering pump, and an anti-backflow structure, and a bubble separation module is provided at the inlet or outlet of the colorimetric detection chamber. The bubble separation module is one or more of the following structures: an expansion chamber, a hydrophobic and breathable membrane, a flow guide baffle, or a slow-flow section.

[0012] Preferably, the optical detection module includes a light source, a collimation component, a detection cell, a main detector, and a reference detector, or includes a sample detection channel and a blank reference channel; The control and data processing module calculates the acetic anhydride content based on the difference, ratio, or correction value between the main detection signal and the reference signal.

[0013] Preferably, the endpoint determination module is used to continuously or intermittently collect detection signals during the color development process, and when the rate of change of absorbance per unit time is lower than a preset threshold and continues to reach a predetermined time, it determines that the color development reaction has reached a stable endpoint and triggers result reading.

[0014] Preferably, the standard addition detection mode includes at least three parallel reaction units. The control and data processing module is used to control the same sample to enter each parallel reaction unit separately, and to add different amounts of standard acetic anhydride solution to different parallel reaction units, so that each parallel reaction unit completes the pre-reaction, color development and optical detection under the same detection procedure, so as to establish a standard addition curve and deduce the acetic anhydride content in the sample.

[0015] A method for detecting acetic anhydride content, applied to the aforementioned optical detection equipment for detecting acetic anhydride content, includes the following steps: S1. Immediately mix ferric chloride non-aqueous solution, perchloric acid-acetic acid solution and hydroxylamine chloride non-aqueous solution to form a pre-reaction solution; S2. Under anhydrous protection conditions, the sample to be tested is added to the pre-reaction solution and a pre-reaction is carried out in the pre-reaction chamber; S3. After the pre-reaction is completed, the pre-reaction solution is introduced into the colorimetric detection chamber and colorimetric water is added quantitatively to form the colorimetric solution. S4. Perform optical detection on the color developing solution and determine the color development endpoint based on the change in the detection signal; S5. Calculate the acetic anhydride content in the sample to be tested using the standard curve method or the standard addition method and output the results.

[0016] Preferably, the mixture of the non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution, and the non-aqueous solution of hydroxylamine chloride satisfies the mass ratio of ferric chloride to hydroxylamine chloride being 1:2-2.5, and the perchloric acid-acetic acid solution accounting for 30%-40% of the total volume of the pre-reaction solution; Before adding the sample to be tested, add methylamine methanol adjustment solution to the pre-reaction solution to make the pH of the system 2-3; After the sample to be tested is added, a pre-reaction period of 10-20 minutes is allowed. Then, colorimetric water is added, with a mass ratio of colorimetric water to hydroxylamine chloride of 20-30:1, and colorimetric detection is performed for 20-30 minutes or the result is read after reaching a stable endpoint.

[0017] The beneficial effects of this invention are: 1. Based on the existing acetic anhydride hydroxylamine-iron colorimetric reaction, this invention changes the traditional manual visual colorimetric method to an optical detection and reading method, which can reduce the influence of ambient light, operator experience, and differences in manual color judgment on the detection results, thereby improving the consistency and digitization of the results output.

[0018] 2. By setting up a reagent instant preparation structure, an anhydrous protection structure, and a segmented structure for pre-reaction and colorimetric detection, this invention transforms the chemical process in the prior art, which is sensitive to the order of liquid addition, low moisture environment, pre-reaction time, and water addition and colorimetric steps, into a process that is controllable by the equipment. This reduces fluctuations caused by manual operation and improves the repeatability and stability of the detection process.

[0019] 3. The present invention sets up a quantitative water introduction and bubble elimination structure, which makes the amount of water added, the mixing state and the detection optical path more stable during the color development stage. This helps to reduce the detection error caused by inconsistent water addition or microbubble disturbance, thereby improving the reliability of optical readings.

[0020] 4. This invention introduces an endpoint determination mechanism. Based on the minimum color development time, it determines whether the color development has reached a stable endpoint according to the trend of absorbance change, instead of simply relying on a fixed waiting time reading. Therefore, it is more conducive to obtaining uniform and comparable test results under different sample conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the optical detection device provided by the present invention; Figure 2 This is a schematic diagram of the reagent flow path and segmented reaction colorimetric structure of the present invention; Figure 3 This is a schematic diagram of the dual-channel detection optical path of the optical detection module of the present invention; Figure 4 This is a flowchart of the standard curve detection mode of the present invention; Figure 5 This is a schematic diagram of the endpoint determination logic of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Please refer to the following: Figure 1 , Figure 2 , Figure 3 , Figure 4 as well as Figure 5 ,in Figure 1 This is a schematic diagram of the overall structure of the optical detection device provided by the present invention; Figure 2 This is a schematic diagram of the reagent flow path and segmented reaction colorimetric structure of the present invention; Figure 3This is a schematic diagram of the dual-channel detection optical path of the optical detection module of the present invention; Figure 4 This is a flowchart of the standard curve detection mode of the present invention; Figure 5 This is a schematic diagram of the endpoint determination logic of the present invention.

[0024] This invention is an improved, equipment-based, and optically-based solution based on the existing acetic anhydride-hydroxylamine colorimetric detection principle. Existing technology has already disclosed that acetic anhydride reacts with hydroxylamine chloride under near-anhydrous conditions to generate isohydroxamic acid, which then forms a red complex with iron ions under acidic conditions. The detection result is obtained by colorimetric comparison with a standard solution. Furthermore, existing technology also discloses that this system is highly sensitive to the order of reagent addition, solution acidity, pre-reaction time, and water addition colorimetric time.

[0025] Example 1 like Figures 1 to 5 As shown, an optical detection device for detecting acetic anhydride content includes a sample quantitative introduction module, a reagent storage module, a reagent instant preparation module, an anhydrous protection module, a pre-reaction module, a colorimetric detection module, a quantitative water introduction module, a bubble elimination module, an optical detection module, an endpoint determination module, a control and data processing module, a result output module, and a waste liquid collection module.

[0026] The sample quantitative introduction module is used to introduce the sample to be tested into the detection system according to a set volume or mass. To ensure repeatability, it is preferred to use a micro-quantitative pump in conjunction with a switching valve to complete the sample introduction. Alternatively, a quantitative loop, injection port, or weighing cup can also be used for sample introduction.

[0027] The reagent storage module is used to store non-aqueous solutions of ferric chloride, hydroxylamine chloride, perchloric acid-acetic acid, methylamine methanol conditioning solution, water for color development, standard acetic anhydride solution, and blank base solution. The non-aqueous solution of ferric chloride can be prepared by dissolving ferric chloride in anhydrous ethanol, with a mass-to-volume ratio of ferric chloride to anhydrous ethanol of 1:100. The non-aqueous solution of hydroxylamine chloride can be prepared by dissolving hydroxylamine chloride in anhydrous methanol, with a mass-to-volume ratio of hydroxylamine chloride to anhydrous methanol of 3:25. The perchloric acid-acetic acid solution can be obtained by measuring perchloric acid and diluting it 100 times with acetic anhydride-free acetic acid, which can be obtained by refluxing acetic acid for 30 minutes. All of the above solution preparation methods are based on existing public knowledge.

[0028] The reagent instant preparation module is connected to the reagent storage module, and at the start of each test, it instantly mixes non-aqueous solutions of ferric chloride, perchloric acid-acetic acid, and hydroxylamine chloride according to a set ratio to form a pre-reaction solution. Preferably, the mass ratio of ferric chloride to hydroxylamine chloride is controlled at 1:2-2.5, and the perchloric acid-acetic acid solution accounts for 30%-40% of the total volume of the pre-reaction solution; more preferably, the mass ratio of ferric chloride to hydroxylamine chloride is 1:2.4. The purpose of instant preparation is to avoid compositional changes caused by prolonged storage of the premixed reaction solution, thereby improving the consistency of the initial state of each test.

[0029] An anhydrous protection module is positioned around the reagent preparation area and the pre-reaction area to provide a low-moisture environment for the pre-reaction stage. This anhydrous protection module can employ one or a combination of several of the following: a sealed housing, a dry gas purging port, a humidity detector, and a desiccant chamber. It is well-established in existing technology that the reaction between acetic anhydride and hydroxylamine chloride is carried out under near-anhydrous conditions; excessive water content in the system will weaken the stability of the colorimetric system.

[0030] The pre-reaction module and the colorimetric detection module are set up separately. The pre-reaction module is used to complete the pre-reaction between the sample to be tested and the pre-reaction solution under low moisture conditions. The colorimetric detection module is used to receive the reaction solution and accept quantitative water addition after the pre-reaction is completed, thereby forming the final colorimetric solution. The pre-reaction module and the colorimetric detection module are connected via a switching valve or a short-path flow channel. The quantitative water introduction module is connected to the colorimetric detection module and is used to add a set amount of colorimetric water to the colorimetric detection module after the pre-reaction is completed. The mass ratio of colorimetric water to hydroxylamine chloride is 20-30:1, more preferably 25:1. In the prior art, this step is usually completed manually; this invention transforms it into an independent quantitative liquid addition action in the equipment.

[0031] A bubble elimination module is installed at the inlet or outlet of the colorimetric detection module to reduce the impact of tiny bubbles introduced during quantitative water introduction and mixing on optical measurements. This bubble elimination module can employ an expanded flow-slowing cavity, a flow-guiding baffle, a hydrophobic and breathable structure, or a flow-slowing channel.

[0032] An optical detection module is positioned on both sides of the detection optical path of the colorimetric detection module, including a light source, collimation structure, detection window, main detection structure, and reference detection structure. During detection, one detection light beam passes through the colorimetric liquid and is received by the main detection structure, while the other reference light beam is received by the reference detection structure. The control and data processing module performs absorbance correction calculations based on the main detection signal and the reference signal. This structure replaces the existing manual visual colorimetric process with an instrumented optical reading process. The endpoint determination module is used to read the absorbance change during the colorimetric process in real time and triggers the final reading when a preset condition is met. Preferably, after meeting the minimum colorimetric time, when the absorbance change rate per unit time is lower than a preset threshold and continues to reach the set duration, the colorimetric process is determined to have reached a stable endpoint. This further improves the fixed placement time in the existing method to a stable endpoint determination under fixed conditions, thereby reducing the impact of sample differences on the reading time.

[0033] The control and data processing module controls sample introduction, immediate reagent preparation, pre-reaction, quantitative water introduction, optical sampling, endpoint determination, concentration conversion, and result output. It also calculates the acetic anhydride content in the sample using the standard curve method or the standard addition method. The result output module displays, stores, or transmits the test results, while the waste liquid collection module collects the acidic organic waste liquid after testing.

[0034] Example 2 This embodiment is used for the direct detection of trace amounts of acetic anhydride in an acetic acid system. During detection, the pre-reaction area is first dried and purged by an anhydrous protection module. Subsequently, a reagent instant preparation module instantly mixes non-aqueous solutions of ferric chloride, perchloric acid-acetic acid, and hydroxylamine chloride to form a pre-reaction solution. Preferably, 10 mL of ferric chloride ethanol solution, 8.05 mL of perchloric acid-acetic acid solution, and 2.08 mL of hydroxylamine chloride methanol solution can be used to form the pre-reaction solution; alternatively, a combination of 10 mL of ferric chloride ethanol solution, 5 mL of perchloric acid-acetic acid solution, and 1.67 mL of hydroxylamine chloride methanol solution can be used. After forming the pre-reaction solution, methylamine methanol adjustment solution is added to adjust the pH of the system to 2-3, preferably to pH 3 or pH 2. Within this range, side reactions of isohydroxyxamic acid that are detrimental to detection accuracy under strong acid or alkaline conditions can be suppressed.

[0035] Subsequently, the sample to be tested is added to the pre-reaction module via the sample quantification introduction module, preferably 50g of the sample. After addition, the sample is mixed at a low speed, preferably not exceeding 40 rpm, and the pre-reaction is maintained for 10-20 min, more preferably 15 min or 20 min. The mass ratio between the sample to be tested and hydroxylamine chloride is preferably controlled at 600-650:3, more preferably 625:3.

[0036] After the pre-reaction is complete, the reaction solution is introduced into the colorimetric detection module, and colorimetric water is added by the quantitative water extraction module. Preferably, the amount of water added can be 7.5 mL, 6 mL, or 4 mL; after color development, it is allowed to stand or slowly mixed for 20-30 min, more preferably 25 min or 30 min. During the color development process, the optical detection module continuously or intermittently acquires detection signals, and the endpoint determination module determines whether a stable endpoint has been reached. When the endpoint reading conditions are met, the control and data processing module reads the final absorbance and uses a pre-established standard curve to calculate the acetic anhydride content. Finally, the result output module outputs the detection result.

[0037] Example 3 This embodiment is used for the detection of samples with matrix interference, and adopts a standard addition method to improve quantitative accuracy.

[0038] During testing, the sample to be tested is first divided into multiple portions, preferably five portions, and then different proportions of standard acetic anhydride solution are added to each portion. Preferably, the amount of standard acetic anhydride added for each portion can be set to 0 ppm, 5 ppm, 10 ppm, 20 ppm, and 50 ppm, respectively. After the standard is added, each portion of the sample enters its corresponding pre-reaction channel and undergoes the same procedure for mixing the pre-reaction solution, adjusting the acidity, adding the sample, performing the pre-reaction, quantitative water extraction and color development, and optical detection. The key point of this setup is that each portion of the sample must have the same reaction process. Finally, a standard curve is plotted between the detection signal generated after the same reaction time and the corresponding added acetic anhydride concentration, and the acetic anhydride content in the sample is calculated based on this curve.

[0039] In this embodiment, the control and data processing module reads the absorbance of each sample at the stable endpoint, uses the added acetic anhydride concentration as the abscissa and the corresponding absorbance or corrected absorbance as the ordinate to perform linear fitting, and deduces the acetic anhydride content in the original sample based on the obtained standard addition curve.

[0040] Example 4 In another embodiment, the optical detection module employs a dual-wavelength detection method. The main detection wavelength is set in the visible light region where the chromogenic complex absorbs strongly, while the reference wavelength is set in the band where the chromogenic complex absorbs weakly but can characterize the sample's background scattering or intrinsic color. The control and data processing module simultaneously acquires the response signals at both the main detection wavelength and the reference wavelength, and calculates the corrected absorbance based on the difference, ratio, or weighted result between the two. This setup can reduce the impact of slight sample turbidity, background color difference, or light source drift.

[0041] Example 5 In another embodiment, the pre-reaction module, colorimetric detection module, bubble elimination module, and waste liquid collection area are integrated into a disposable reaction cartridge. This reaction cartridge has multiple inlet ports for connecting sample solution, non-aqueous ferric chloride solution, perchloric acid-acetic acid solution, non-aqueous hydroxylamine chloride solution, methylamine methanol conditioning solution, colorimetric water, and standard acetic anhydride solution, respectively. After detection, the entire reaction cartridge can be removed and replaced to reduce cross-contamination, making it suitable for batch detection or online rapid quality control scenarios.

[0042] Example 6 In another embodiment, the control and data processing module has two preset detection modes: a standard curve detection mode and a standard addition detection mode. For samples with lighter colors and simpler matrices, the standard curve detection mode is used; for samples with darker colors, higher viscosity, or significant matrix effects, the standard addition detection mode is used. This configuration balances the device's rapid detection capabilities with the quantitative accuracy of complex samples.

[0043] In the above embodiments, the preparation methods of ferric chloride non-aqueous solution, hydroxylamine chloride non-aqueous solution, and perchloric acid-acetic acid solution, as well as the mass ratio of ferric chloride to hydroxylamine chloride, the volume fraction of perchloric acid-acetic acid solution, the pH control range, the pre-reaction time, the water addition and color development time, the water addition ratio, and the standard addition concentration settings, are all based on existing public information. The improvement of this invention lies in transforming these chemical conditions into a controllable equipment structure and an automated detection process.

[0044] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An optical detection apparatus for detecting acetic anhydride content, characterized by comprising: include: The sample quantitative introduction module is used to quantitatively introduce the sample to be tested; The reagent storage module is used to store non-aqueous solutions of ferric chloride, non-aqueous solutions of hydroxylamine chloride, perchloric acid-acetic acid solution, conditioning solution, colorimetric water, standard acetic anhydride solution, and blank base solution, respectively. The reagent instant preparation module is used to mix the non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution and the non-aqueous solution of hydroxylamine chloride in a set ratio to form a pre-reaction solution at the start of the detection. Anhydrous protection module is used to keep the pre-reaction stage in a low-moisture interference environment; The segmented reaction colorimetric module includes a pre-reaction chamber and a colorimetric detection chamber. The pre-reaction chamber is used to perform a pre-reaction with the sample to be tested and the pre-reaction solution. The colorimetric detection chamber is used to receive the reaction solution after the pre-reaction and form a colorimetric solution after adding colorimetric water. The quantitative water introduction module is used to add a set amount of colorimetric water to the colorimetric detection chamber after the pre-reaction is completed; The optical detection module is used to perform absorption optical detection on the colorimetric solution and output a detection signal; The endpoint determination module is used to determine whether the colorimetric reaction has reached a stable endpoint based on the changes in the detection signal. The control and data processing module is used to control the coordinated operation of each module and to calculate the acetic anhydride content in the sample to be tested based on the detection signal. The result output module is used to output the detection results; The control and data processing module includes at least a standard curve detection mode and a standard addition detection mode.

2. The optical detection apparatus for detecting acetic anhydride content according to claim 1, characterized by, The reagent instant preparation module includes a multi-channel micro-metering pump, a switching valve, a manifold node, and a mixing channel. The non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution, and the non-aqueous solution of hydroxylamine chloride are instantaneously mixed at the manifold node to form a pre-reaction solution before entering the pre-reaction chamber.

3. The optical detection apparatus for detecting acetic anhydride content according to claim 1, characterized by, The anhydrous protection module includes a sealed housing and at least one of a drying gas interface, a desiccant chamber, and a humidity detection unit disposed on the sealed housing. The reagent instant preparation module and the pre-reaction chamber are disposed inside the sealed housing.

4. The optical detection apparatus for detecting acetic anhydride content according to claim 1, characterized by The pre-reaction chamber and the colorimetric detection chamber are set independently and connected by a switching valve or a connecting microchannel. The pre-reaction solution completes the contact reaction between the sample to be tested and the pre-reaction solution in the pre-reaction chamber before being introduced into the colorimetric detection chamber. The colorimetric water is added only in the colorimetric detection chamber.

5. The optical detection device for detecting acetic anhydride content according to claim 1, characterized in that, The quantitative water intake module includes an independent water path, a micro-metering pump, and an anti-backflow structure. A bubble separation module is provided at the inlet or outlet of the colorimetric detection chamber. The bubble separation module is one or more of the following structures: an expansion chamber, a hydrophobic and breathable membrane, a flow guide baffle, or a slow-flow section.

6. The optical detection device for detecting acetic anhydride content according to claim 1, characterized in that, The optical detection module includes a light source, a collimation component, a detection cell, a main detector, and a reference detector, or it may include a sample detection channel and a blank reference channel. The control and data processing module calculates the acetic anhydride content based on the difference, ratio, or correction value between the main detection signal and the reference signal.

7. The optical detection device for detecting acetic anhydride content according to claim 1, characterized in that, The endpoint determination module is used to continuously or intermittently collect detection signals during the color development process, and when the rate of change of absorbance per unit time is lower than a preset threshold and continues to reach a predetermined time, it determines that the color development reaction has reached a stable endpoint and triggers result reading.

8. The optical detection device for detecting acetic anhydride content according to claim 1, characterized in that, The standard addition detection mode includes at least three parallel reaction units. The control and data processing module is used to control the same sample to enter each parallel reaction unit separately, and to add different amounts of standard acetic anhydride solution to different parallel reaction units, so that each parallel reaction unit completes the pre-reaction, color development and optical detection under the same detection procedure, so as to establish a standard addition curve and deduce the acetic anhydride content in the sample.

9. A method for detecting acetic anhydride content, characterized in that, The optical detection device for detecting acetic anhydride content according to any one of claims 1 to 8 comprises the following steps: S1. Immediately mix ferric chloride non-aqueous solution, perchloric acid-acetic acid solution and hydroxylamine chloride non-aqueous solution to form a pre-reaction solution; S2. Under anhydrous protection conditions, the sample to be tested is added to the pre-reaction solution and a pre-reaction is carried out in the pre-reaction chamber; S3. After the pre-reaction is completed, the pre-reaction solution is introduced into the colorimetric detection chamber and colorimetric water is added quantitatively to form the colorimetric solution. S4. Perform optical detection on the color developing solution and determine the color development endpoint based on the change in the detection signal; S5. Calculate the acetic anhydride content in the sample to be tested using the standard curve method or the standard addition method and output the results.

10. The method for detecting acetic anhydride content according to claim 9, characterized in that, The mixture of the non-aqueous solution of ferric chloride, the perchloric acid-acetic acid solution, and the non-aqueous solution of hydroxylamine chloride satisfies the following mass ratio: ferric chloride to hydroxylamine chloride 1:2-2.5, and the perchloric acid-acetic acid solution accounts for 30%-40% of the total volume of the pre-reaction solution; Before adding the sample to be tested, add methylamine methanol adjustment solution to the pre-reaction solution to make the pH of the system 2-3; After the sample to be tested is added, a pre-reaction period of 10-20 minutes is allowed. Then, colorimetric water is added, with a mass ratio of colorimetric water to hydroxylamine chloride of 20-30:1, and colorimetric detection is performed for 20-30 minutes or the result is read after reaching a stable endpoint.

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